1. Field of the Invention
The invention relates to a system or a tool or an insert for the removal of a defect in a tooth or for making a cavity in a tooth.
There are various causes which justify the making, by machining involving the removal of material, of a cavity in a tooth and the repair of the tooth by means of a treatment of the cavity. Such a measure may be effected e.g. for aesthetic reasons to remove an unsatisfactory form of a part of the tooth. In most cases, however, these measures are carried out for repairing an unhealthy tooth, namely for removing a carious defect. A further reason for a measure as described above can also be the exchange of tooth fillings which are unsatisfactory for a variety of reason.
2. Description of the Related Art
In DE 42 09 191 A1 there are described a device and a process for the treatment of natural hard tissue with the employment of oscillating tools. With this known device, to make an occlusal cavity, a tool is used which has at its surface geometrically defined cutting edges or has cutting edges of non-defined geometric form such as adherent diamond grains, which make possible working of the material of the tooth, with the removal of material, with the oscillating movement of the tool. With the tool, there is made a cavity having an inwardly converging peripheral wall the cross-sectional size of which is a multiple of the cross-sectional size of the tool and the cross-sectional form of which differs substantially from the cross-sectional form of the tool. The tool is held releasably in a handpiece by means of a mounting device. The tool has a fluid outlet, at a spacing to the rear from the handpiece head which receives the tool, through which outlet a flow of fluid, e.g. water or a saline solution, can be directed at the treatment site and onto the tool for the purpose of cooling and rinsing. Measures for filling the cavity and treating the tooth are not described in this document. This known device and this known process are not only work and time consuming so far as the preparation of the cavity is concerned but also with regard to the usual methods of filling the cavity, whereby in this respect demands are made on the practicability of the preparation work and treatment work, on the thereby necessary manipulability, on the firmness and load bearing and on the lifetime of the treatment.
The above described treatment measures in a tooth occur not only in its occlusal region but also in its lateral and approximal region. In particular approximal preparations and treatments are difficult to carry out because of a neighbouring tooth and the thus resulting restricted accessibility, whereby there is a danger of damage to the neighbouring tooth.
The treatment of a cavity with a laboratory-prepared inlay is work-intensive and correspondingly expensive. Further, the tooth to be treated can be definitively treated only in a second treatment session and thus with "double time". To reduce the outlay involved in a treatment, it has already been proposed to use inlays manufactured at the place of treatment, as is e.g. possible with the so-called computer controlled milling of inlays. Further, it has already been proposed to use for the treatment of cavities prefabricated inlays, whereby likewise a treatment in only one treatment session and thus at a "single time" is possible. With such a measure, however, special preparation and treatment measures are needed which are again time consuming and involve complicated manipulation and are expensive.
The object of the invention is to improve a system, an insert or a tool for removing a defect in a tooth.
According to one aspect of the invention, there is provided a material removing tool for working on a tooth to make a tooth cavity by oscillating movement, such tool comprising a shaft and an abrasive treatment section and characterized in that the abrasive section is formed by a working head having an abrasive working surface and an opposing smooth surface.
According to another aspect of the invention, there is provided novel insert for filling a cavity on a tooth which has been worked using an oscillatingly moveable tool, wherein the body of the insert is pre-fabricated so that its surface area enclosed by the cross-sectional walls of the cavity of its entire cross-sectional area is adapted to the cross-sectional dimension and shape of the tool and comprises bearing surfaces for abutting diverging edge surfaces on the cavity.
With the system in accordance with the invention there are employed a tool working in an oscillating manner for the preparation of a cavity, and an insert which can be inserted into the cavity, which are matched one to the other at least in the region which is defined by the tooth wall of the cavity surrounding the insert. By these means it is possible to prepare an exactly matched cavity and to treat the tooth without needing to direct special attention the matching form of the cavity and the insert. This is provided in that a tool working in an oscillating manner is used which, because of the oscillation, is independent of a rotational movement and thus can be manufactured in selected forms. With all these forms there can be produced in the tooth, in a simple manner, by machining involving the removal of material, a cavity corresponding to the form of the tool. The tool need only be sunk, oscillating, into the tooth material. Thereby a particular form for the cavity is automatically achieved. Thus, in that in accordance with the invention an insert is employed which is matched to the form and size of the tool at least in the region formed by the walls of the cavity, no special measures are needed for matching the form of the cavity to the insert, since agreement is reached automatically. The term agreement is to be understood in the sense that the form and size of the insert, taking into account a small amount of play or a small gap, correspond to the related form and size of the tool or of the cavity. Such an amount of play can be provided as a small difference in size or this amount of play can be provided automatically because of the oscillating movement of the tool. Such an amount of play is necessary in order to be able to place the insert into the cavity without jamming. Thereby, it is to be taken into the consideration that because of the roughness of the wall surfaces of the cavity a certain amount of play is of advantage. Further, the amount of play or the gap is needed to be able to place therein plastic and curing or hardening bonding material and to ensure on the one hand a firm and on the other hand a sealed bond between the tooth and the insert.
The invention thus makes possible a simple, readily manipulable treatment of a tooth that can be rapidly carried out, which is not only economical but also of particular quality with regard to its firmness and load bearing and lifetime.
The system in accordance with the invention is suitable particularly advantageously for a treatment in the inaccessible approximal region of the teeth. Thereby, damage to the neighbouring teeth can be avoided since those surfaces of the tool which in the course of preparation come into contact with the neighbouring tooth surface are not configured for removing material.
The surfaces of the tool and the associated insert which do not belong to the region which is defined by means of the wall surfaces of the cavity need not to be adapted one to the other in the above-described sense. When such a region surface is a lateral or approximal surface of the insert this can likewise be pre-fabricated e.g. in an idealized form. In the occlusal region of a purely occlusal or also lateral or approximal cavity, the insert may be larger than is necessary and after attachment in the cavity may be adapted through machining involving removal of material. This is naturally true also for a lateral surface of the insert. Within the scope of the invention it is however also possible to provide the vertical dimension for an occlusally open cavity smaller than the necessary dimension and after attachment of the insert in the cavity to complete this dimension by means of a building up of material, e.g. at the same time as a region extending to a neighbouring or to the other occlusal region of the tooth.
It is advantageous to provide at a treatment station a plurality of tools and a plurality of mold parts adapted thereto in the sense in accordance with the invention, which with regard to their size in one and/or both dimensions, their cross-sectional form and/or their height and/or their coloring are different. By these means it is not only possible to use for a particular size of the defect a correspondingly dimensioned tool and also an associated insert, but it is also possible to make a cavity through the use one after another of progressively larger tools in a plurality of working steps.
A further advantage of the invention consists in forming mutually oppositely lying surfaces of the tool convergingly in the forward driving direction of the tool so that the tool worked into the tooth material can be withdrawn from the thus formed cavity without jamming.
Further, the invention relates also to a tool and an insert having the features in accordance with the invention. The above described advantages apply also to the tool and the insert part.
The invention relates also to a process for removal of a defect in a tooth which is advantageous for the same or corresponding reasons.